Good, but still plenty of room for improvement.
I'll just go ahead and list the areas that I think need improvement..
The Spherical drones that fly and zap you move FAR too fast. Especially since they tend to zone in straight on you occasionally causing you to crash into them. Was rather difficult the first time I fought them because they'd zoom from the end of the screen to me before I even realized it.
The Carriers were HORRIBLY annoying. They spawned far too many enemies quickly, and the level which consisted of nothing but carriers was rather difficult. Not because they're hard to kill, but rather because often you'll grab a freshly spawned enemy instead of the carrier itself.
The upgrades don't really feel like they do much. I never really noticed much of an improvement in damage for any of the upgrades no matter how much I upgraded them. Well, not until I took on earlier enemies. But as the levels progress it feels kind of like my damage stagnated. It'd take forever to kill the enemies. And when your main weapon consists of grabbing and holding an enemy till its dead.. It can kind of get over whelming when you can only hold two at a time, and they're not dieing fast enough. Mind you, this was with everything at roughly 7 at the least. And things just.. didn't die fast enough. Most notably the enemies that fired two bullets at once.
And now my biggest complaint? Enemies attacking from offscreen. There seems to be a rather large area which the player simply isn't allowed to see on the edges of the screen. And quite often enough, you'll have enemies staying off screen and attacking. Usually giving them enough time to get three or four shots off before they appear. This is only minorly annoying with the normal enemies, but when the carriers appear, it means that they'll spawn AT LEAST three new enemies for you to fight before theres even a chance they'll appear. To say thats aggrivating would be an understatement.
Next complaint might not be legitimate, but I found the damage for bumping into enemies to be rather.. high. Especially later ones. I say it may not be legitimate because I frankly didn't upgrade my defense much, so I don't know if thats cause of that or not.